This invention relates to multi-phased motor drives and, more particularly, to a multi-phase motor drive including coil magnets and transistors arranged in an electric circuit matrix.
Electric multi-phase motors are widely used in such applications as pumps and compressors. A typical multi-phase motor drives a rotor or multiple rotors in response to magnetic fields selectively generated by coil magnets. Each coil magnet is in electrical communication with a motor drive, which selectively energizes the coil magnets to produce the magnetic fields that drive the rotors. The rotors drive a fluid, such as air or hydraulic fluid, from an intake to a discharge.
Disadvantageously, the full force of the magnetic flux generated by the coil magnets act on the rotors when the coil magnets are energized using these conventional motor drives. This causes a jerking type rotor movement, which may reduce efficiency. This is most evident at relatively low rotor speeds. For example, if each coil magnet of a nine coil magnet multi-phase motor is turned on for one second, one cycle of the rotor would then take nine seconds. The time for the rotor to move between magnets may only take one tenth of a second. For the other nine tenths of a second, the rotor would be stopped. This type of motor drive control is relatively inefficient as the rotor loses inertial energy during starts and stops.
Typical motor drives are configured such that each coil magnet is connected between two transistor switches. In one example having three coil magnets, each of the coil magnets is electrically connected between a low side transistor and a high side transistor. The low side transistors are connected to the negative DC bus ground and the high side transistors are connected to the positive DC bus. To energize a selected coil magnet, the associated low side and high side transistors are turned on to open an electrical connection. Other conventional examples that include additional coil magnets require additional high and low side transistors for each additional coil magnet. Utilizing two transistors for each coil magnet proportionately increases the expense of the multi-phase motor drive system.
Accordingly, a motor drive system that utilizes less than a pair of transistors for each coil magnet while more efficiently controlling movement of the rotor(s) is needed.